Suspension

MOST MANUFACTURERS EMPLOY ONE BASIC SUSPENSION SYSTEM TO HANDLE A WIDE VARIETY OF DUTIES—EVERYTHING FROM COMPETITIVE XC RACING TO AGGRESSIVE ALL-MOUNTAIN RIDING. THEY TAKE ONE DESIGN AND APPLY IT TO DIFFERENT BIKES BUILT FOR DIFFERENT PURPOSES BY MODIFYING THE REAR SHOCK AND LENGTH OF TRAVEL.

That’s one way to do it. But Felt engineers, accustomed to fine-tuning the designs of different bikes to meet precise performance goals, have taken an alternate approach; just as they wouldn’t accept using a road fork for a triathlon bike, they felt a lightweight XC racing bike has different suspension needs than a trail bike.

That’s why Felt has two different suspension systems—FAST for competitive XC and Equilink for marathon, trail or all-mountain riding. Each is designed to optimize the bike it’s paired with. FAST places great emphasis on ultra low weight, integration with a carbon rear triangle and pedaling efficiency. Equilink delivers a supple, active feel for rugged terrain plus incredible traction and braking control. Both are designed to make every off-road ride the best it can possibly be.

FAST

To meet the lofty standards of cross country racers on the Felt Ötztal X-Bionic Team and Team Kenda-Felt, engineers created an entirely new suspension system called Felt Active Stay Technology, or FAST. Offering 100 millimeters of smooth, predictable travel, FAST delivers unmatched performance in a lightweight, race-ready package.

FAST is about efficiency. It’s about soaking up the terrain and keeping your tires on the ground for the improved traction and handling needed in XC racing conditions.

The genius behind FAST is its simplicity. By creating a frame and suspension system that work in unison to achieve specific goals— namely, XC speed, control and efficiency—Felt engineers were able to pinpoint their efforts. FAST makes the most of the Felt’s considerable experience working with cutting-edge materials and construction techniques, and utilizes the design of the frame to optimize the bike’s overall suspension performance.

“FAST suspension technology embodies a light, stiff carbon fiber rear triangle assembly that doubles as a secondary spring assist to the rear suspension,” says Felt suspension engineer Mike Ducharme.

As Ducharme points out, one of the keys to FAST is the innovative rear stays. The carbon fiber seatstay and chainstay work together like a leaf spring, offering just enough flex to optimize rear suspension activity. The whole rear end is custom shaped and engineered to provide both a stable pedaling platform and a smooth trail feel. It helps keep your tires on the ground when climbing or pedaling through smaller stutter bumps—situations where suspension affects traction—and adds just enough compliance to reduce fatigue over long efforts such as marathon or 24-hour races.

FAST takes cues from the single-pivot suspension design that performance-minded XC riders favor because of light weight and reliability, and optimizes this tried-and-true system with a few new twists. It utilizes a set of carbon fiber stays that flex evenly throughout the suspension travel, providing performance characteristics that mimic much more complicated suspension systems—but without the extra weight and complexity.

“This design not only eliminates the need for an additional pivot in the assembly, but also acts to hold the suspension at the optimal ride/race geometry,” says Ducharme. “We were able to decrease the weight and increase efficiency by designing out unnecessary hardware and reducing unwanted suspension bob without sacrificing small bump compliance.”

The stays are designed to be neutral (in their natural shape) at the “sag point” because that’s where the bike typically rests under rider weight. The shock spring is supplemented by the design and material of the rear stay, which acts as a leaf spring, stiffening the latter part of the suspension travel. The slight additional spring provided by the carbon stay helps keep the suspension sitting at the proper sag point, which reduces small inputs from the rider that would cause unwanted bobbing from the suspension. This design eliminates the need for a mechanical lockout or an overly damped shock that requires extra force to be “opened.” The end result of all this: minimized bob without any harshness.

The construction and mechanical aspects of the FAST system reveal an obsessive eye for detail. Every last fitting has been scrutinized and selected for durability and weight reduction. The two main pivots feature sealed cartridge bearings for smooth performance, and there’s a unique “link axle” system for the shock links that reduces weight by using less steel hardware and a hard anodized axle for the shock links’ bearings to roll on. A “DU” bearing (similar to what

is found in shock eyelets) and titanium axle are used for the less- stressed seatstay pivot. Besides shedding precious grams, this pivot construction proved its durability in testing.

The result is incredible performance and extremely light weight – the recipes for racing success. FAST-equipped bikes have already taken major victories in at the highest level of the sport in both Europe and the U.S. Built specifically for the Edict Series, FAST is exactly what the XC racer, be it a short-track sprint fiend or an all-day marathon racer, demands in a bike.

EQUILINK

This is the award-winning suspension system for Felt’s Virtue Series trail bikes. For riders ranging from marathon XC racers to those looking to tackle more aggressive terrain, the active yet efficient feel offered by Equilink is the perfect choice.

Many suspension systems require the bike to have a solid rear triangle, but Equilink ties the upper and lower suspension links together so neither can move without affecting the other. Under power, chain tension tries to pull the lower link down while the other wants to pivot up. However, by connecting the two, those opposing forces merely create a bit of tension in the Equilink and effectively cancel each other out. Moreover, the Equilink is oriented nearly perpendicular to the direction of the chain, negating its effects even further.

Think of it as a tug-of-war between equally matched foes. Each wants to go in their own direction but the rope keeps either from gaining any ground. As such, chain tension produces no suspension movement whatsoever and you rocket forward on the trail with maximum pedaling efficiency.

Chain tension isn’t the only force at play here, though. As you accelerate, your body weight tends to move toward the rear of the bike, creating a suspension phenomenon commonly referred to as squat. The idea is simple: shift your weight rearward and you increase the load on the suspension, thus inducing movement. When this occurs, you’re wasting precious watts.

Felt engineers solved this by tweaking the anchoring positions on the upper and lower links. After countless design iterations they settled on positions that cause the Equilink to tug just a bit harder on the upper link than the lower. As a result, the system neutralizes the negative effects of both chain tension and weight shift.

And what about braking effects? Poorly designed systems can produce squat (suspension compression) or jack (suspension extension) when the rear brake is applied, either of which can disrupt how the rear wheel tracks the ground. With Equilink, braking forces are directed down into the stay and are resisted by the long lever arm defined by the dropout pivot and lower suspension linkage. Apply the brakes and the Equilink rear end slows you down while keeping the wheel firmly planted on the ground.

So Equilink effectively counteracts all of the negative forces acting on the system, thus leaving the rear suspension to absorb trail impacts of all shapes and sizes. Since the rear shock isn’t required to do double duty to produce a stable pedaling platform, we are able to tune the shocks to produce the plushest possible feel.

Perfectly engineered suspension rates and a low-leverage design offer the same buttery ride quality on small, medium and big hits alike. Moreover, Equilink’s ever-so-slightly rearward axle path allows the rear wheel to move up and back to better absorb square-edged hits, yet is close enough to vertical that it doesn’t produce any noticeable pedal kickback.

Equilink is also extremely tolerant of a wide range of shock settings as there is no single sweet spot. Add more pressure if you want a firmer feel or dial it back to soften things up. Either way, you still get the same superior pedaling performance.

To keep the rear end of Equilink-equipped bikes true and durable, Felt uses stiff carbon or aluminum rear triangles, cromoly thru-bolts, stainless steel hardware and oversized frame sections to eliminate any unwanted movement.

Different suspension systems for different bikes. It’s not the simplest approach, but it is the most precise. And when it comes to performance, Felt won’t compromise.